Chassis part consisting of fiber-reinforced plastics, equipped with an integrated sensor

ABSTRACT

The present invention pertains to a chassis part for connection and force transmission between a vehicle chassis of at least one wheel, consisting of fiber-reinforced plastics or plastic composite systems, preferably for a passenger car or utility vehicle. 
     The present invention is characterized in that at least one means for measuring forces acting on the chassis parts is integrated in the plastic portions of the chassis parts.

FIELD OF THE INVENTION

The present invention pertains to chassis parts for connection and forcetransmission between a vehicle chassis and at least one wheel,consisting of fiber-reinforced plastics or plastic composite systems,preferably for a passenger car or utility vehicle.

BACKGROUND OF THE INVENTION

Such chassis parts for connection and force transmission between thevehicle chassis and the wheel, also called control arms, are known, inprinciple. Furthermore, it has been known, e.g., from DE 38 39 855 A1that lightweight components comprising a connection between structuralparts made of metal and plastic can be manufactured. It is problematicin such composite materials that the plastic portions, especiallyfiber-reinforced plastic components, may undergo brittle fracture underexcessively high loads. This means that such parts may abruptly losetheir strength and stability under an excessively high load. The use ofsuch composite materials in chassis control arms therefore represents acertain safety hazard, because, on the one hand, extremely high safetyrequirements are imposed in such environments, but enormous forces maybriefly act on the chassis control arms because of unpredictable drivingsituations or accident situations. However, such composite materialsmake possible an extremely low-weight and consequently energy-savingdesign, so that it is desirable for reasons of the efficient manufactureof vehicles to use such composite materials in chassis control arms aswell.

SUMMARY OF THE INVENTION

The object of the present invention is therefore to design theabove-mentioned chassis parts such that a hazard-free and risk-free usein vehicles is possible.

According to the invention, a chassis part for connection and forcetransmission between a vehicle chassis and at least one wheel of a motorvehicle is provided consisting of fiber-reinforced plastics or plasticcomposite systems. At least one device for measuring forces acting onthe chassis part is integrated in the plastic portion (fiber-reinforcedplastics or plastic composite systems portion) of the chassis part.

The device or devices for measuring the acting forces may be a wirestrain gauge, a piezo element, an acceleration sensor or a fiber-opticlight guide embedded in the plastic (fiber-reinforced plastics orplastic composite systems) of the chassis part.

The device or devices for measuring the acting forces are arranged suchthat they can record forces along at least two and preferably threeindependent axes.

The device or devices for measuring the acting forces may be coupledwith an electronic control device for stabilizing the driving and/or theposition of the vehicle, especially by action on driving or brakingelements (e.g., ESP). The device or devices for measuring the actingforces may be coupled with an electronic documentation device for themeasured forces. The electronic documentation device may be integratedwithin the electronic control device for stabilizing the driving and/orthe position of the vehicle. The documentation device may have a warningdevice to provide an alert as to when preset maximum loads and/or theservice life are exceeded. The documentation device may have means forlocking the vehicle when preset maximum loads are exceeded.

According to another aspect of the invention, a method of use of achassis part is provided. A device or devices are integrated in thechassis parts made of plastic or composite materials for measuringforces acting on the chassis parts. The method includes checking theservice life of these chassis parts and collecting measured values forelectronic control devices, especially for the headlight levelingcontrol and/or for the stabilization of the driving and the position ofa vehicle.

The inventors have recognized that it is possible to recognize symptomsof fatigue in time by the continuous monitoring of the forces occurringin these chassis parts and thus to guarantee sufficient safety duringthe use of composite materials for such chassis parts. Since plasticshave a substantially greater elongation than metals at equal strength,these materials are especially suitable for determining the loadactually acting on them simply and accurately by means of wire straingauges or piezo elements. Since integration over time is also possible,it is also possible to detect symptoms of material fatigue that aregenerated not only by peak loads but also by permanent loads. Moreover,it proved to be especially advantageous that not only are forcemeasurements possible as a result for monitoring the service life ofthese chassis parts, but the measured force values can also be utilizedin electronic control devices, preferably for stabilizing the driving orposition of vehicles.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its uses,reference is made to the accompanying drawings and descriptive matter inwhich a preferred embodiment of the invention is illustrated.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a sectional view of a chassis part for connection and forcetransmission between a vehicle chassis and at least one wheel of a motorvehicle and with a device for measuring forces acting on the chassispart.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawing in particular, corresponding to the idea of thepresent invention, an improved chassis part 10 is provided forconnection and force transmission between a vehicle chassis and at leastone wheel. The chassis part 10 consists of fiber-reinforced plastics orplastic composite systems 12. The chassis part 10 is preferably for apassenger car or a utility vehicle. A measuring device 14 or means formeasuring forces acting on the chassis part is integrated in the plasticportions of the chassis part 10.

Chassis parts such as chassis part 10 are basically lever constructions,which are also subject to higher loads and especially accelerations thanthe rest of the vehicle in a jerky and shock-like manner, especially ifthey are so-called control arms. When these accelerations occur they canbe measured with an acceleration sensor. If we now assume that certainaccelerations over a defined period of time describe a path traveled,abuse of the control arm, e.g., high-speed travel over a curb, can beinferred. Even though this is not a direct force measurement, it isnevertheless sufficient for identifying states of abuse.

As was mentioned above, measuring device 14 may be one or more wirestrain gauges or piezo elements embedded or integrated in the plasticmaterial 12, by means of which the forces occurring and acting on thechassis part 10 can be determined in an electronic manner. These morewire strain gauges or piezo elements may be used in this situation toparticular advantage.

In a special design of the chassis part 10 according to the presentinvention, the means for measuring the acting forces 14 are arrangedsuch that they can record forces along at least two and preferably threeindependent axes 14X, 14Y and 14Z (see FIG. 1). As a result, it ispossible to define the acting forces either in one plane or even inspace.

Another manner of measuring the load acting on a force connection strutmay be to provide the measuring device 14 as an embed fiber-optic lightguide in the plastic material 14 of the chassis part 12, in which casethe transmission changes in individual modes as soon as the plastic isbent under load. Thus, the bending stress in the control arm can beinferred from the measurement of frequency band shifts, e.g., theextinction of individual modes.

Corresponding to the basic idea of the present invention, the inventionalso provides a vehicle with the above-mentioned chassis parts, whereinat least one means for measuring the acting forces is coupled with anelectronic control device 16 for stabilizing the travel and/or theposition of the vehicle, especially by acting on driving or brakingelements. Such control devices may be, e.g., the prior-art ESP(Electronic Stability Program) or even a simple headlight levelingcontrol of the vehicle headlights.

Furthermore, a vehicle according to the present invention may bedesigned such that at least one means for measuring the acting forces 14is coupled with an electronic documentation device 18 for the measuredforces as part of the control device. This electronic documentationdevice 18, which comprises, e.g., a simple electronic memory, in whichthe measured values are stored electronically, now also makes itpossible to recognize loads that occur later. Another possibility is toalso carry out an evaluation of the measured values, e.g., with respectto the maxima read out, or a more complex calculation of an integratedload and consequently of the life expectancy still present, in theelectronic documentation device. This may possibly also be performedcombined with a temperature sensor, because there likewise aredependencies between the strength of the particular chassis part and thecurrent body temperature of the chassis part, which should be taken intoaccount especially in case of the use of plastics. The load-bearingcapacity of plastics has a substantially stronger temperature dependencethan metals.

It is especially advantageous in the sense of the idea of the presentinvention if the electronic documentation device 18 is integrated in theelectronic control device 18 for stabilizing the driving and/or theposition of the vehicle. This leads to the possibility of having tocalculate the currently occurring forces only once and to use them atthe same time for the life expectancy, on the one hand, and forstabilizing the driving and/or the position of the vehicle, on the otherhand.

Since information is obtained on the durability of the chassis partbased on the knowledge of the loads on the corresponding chassis part10, it may, furthermore, be advantageous to provide means for warning 20when preset maximum loads are exceeded and/or a maximum service life hasbeen reached. The measured data are consequently used for twoapplications at the same time. This results in a synergistic effect dueto the elimination of the need for additional sensors for controllingthe overload on the control arm or for the determination of the chassisparameters for an electronic drive or position stabilization.

In a continuation of this idea of the present invention, the inventorspropose, furthermore, that the documentation device also have means forlocking 22 to lock the vehicle when the above-mentioned preset maximumloads or the maximum service life of an essential chassis part areexceeded.

Due to the outfit of chassis parts according to the present invention,it is now also possible to manufacture control arms that are relevantfor safety from fiber-reinforced plastics and to use them without safetyhazards. If the control arms are manufactured according to an injectionmolding process or an RTM-like process (RTM=Resin Transfer Molding), theintegration of prefabricated sensors 14 as inserts can be accomplishedvery easily. Control arms from other materials or material compositesystems, which have a high local elongation due to their design, aresuitable as well. Sensors 14 can be integrated in this case in thecontrol arm in a simple manner in appropriate areas, e.g., where highlocal loads occur. The sensors may assume two functions, namely, theymay be used, on the one hand, for the continuous measurement of theforces and consequently for providing data for an electronic chassiscontrol, and, on the other hand, for monitoring to show whetheroverloads that could damage the control arm itself occur.

The information that makes possible the diagnosis of the state of thechassis is thus made available by the process described. In particular,such a diagnosis may be meaningful after accidents, in which, e.g., novisible damage can be recognized on chassis parts, but it may be assumedbased on the forces measured that structural damage must have occurredinside such parts.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

1. A chassis part for connection and force transmission between avehicle chassis and at least one wheel of a motor vehicle, the chassispart comprising: a plastic portion consisting essentially offiber-reinforced plastics or plastic composite systems defining acontrol arm; at least one measuring means for measuring forces acting onthe chassis part, said measuring means being integrated in the plasticportion of the chassis part; an electronic documentation device whereinsaid measuring means is coupled with said electronic documentationdevice for receiving the measured forces; and a temperature sensorwherein coupling said measuring device with said electronicdocumentation device for the measured forces includes evaluating themeasured values in the electronic documentation device based on thetemperature sensed by the temperature sensor, further wherein thecontrol arm consists of fiber-reinforced plastics or plastic compositesystems.
 2. A chassis part in accordance with claim 1 above, wherein atleast one means for measuring the acting forces is a wire strain gauge.3. A chassis part in accordance claim 1, wherein the means for measuringthe acting forces are arranged such that they can record forces along atleast two-axes.
 4. A chassis part in accordance with claim 1, whereinthe means for measuring the acting forces is arranged so as to recordforces along at least three independent axes.
 5. A chassis partaccording to claim 1, wherein the control arm consists offiber-reinforced plastics.
 6. A chassis part in accordance with claim 1above, wherein at least one means for measuring the acting forces is apiezo element.
 7. A chassis part in accordance with claim 1 above,wherein at least one means for measuring the acting forces is anacceleration sensor.
 8. A chassis part in accordance with claim 1 above,wherein at least one means for measuring the acting forces is afiber-optic light guide embedded in the plastic of the chassis part. 9.A vehicle with a chassis part, the vehicle comprising: a chassis partcontrol arm with a plastic portion consisting essentially offiber-reinforced plastics or plastic composite systems and at least onemeasuring means for measuring forces acting on the chassis part, saidmeasuring means being integrated in the plastic portion of the chassispart; and an electronic control device for stabilizing the drivingand/or the position of the vehicle by action on driving or brakingelements, said electronic control device being coupled to said measuringmeans; an electronic documentation device wherein said measuring meansis coupled with said electronic documentation device for the measuredforces; and a temperature sensor wherein coupling said measuring meanswith said electronic documentation device for the measured forcesincludes evaluating the measured values in the electronic documentationdevice based on the temperature sensed by the temperature sensor.
 10. Avehicle in accordance with claim 9, wherein the electronic documentationdevice is integrated within said electronic control device forstabilizing the driving and/or the position of the vehicle.
 11. Avehicle in accordance with claim 9, wherein the documentation device hasmeans for warning when preset maximum loads and/or the service life ofsaid chassis part are exceeded.
 12. A vehicle in accordance with claim9, wherein the documentation device has means for locking the vehiclewhen preset maximum loads are exceeded.
 13. A method of using a chassispart, the method comprising: providing the chassis part as a control armpart made of plastic or composite materials with an integrated measuringdevice for measuring forces acting on the chassis part; measuring forcesacting on the control arm part using the integrated measuring deviceproviding a temperature sensor for temperature measurement in the regionof the control arm; providing an electronic documentation device;coupling the measuring device with the electronic documentation devicefor the measured forces; and evaluating the measured values in theelectronic documentation device based on the temperature sensed by thetemperature sensor.
 14. A method according to claim 13, furthercomprising: checking the service life of these chassis part based on themeasured forces.
 15. A method according to claim 13, further comprising:collecting measured values and providing the values to an electroniccontrol device for one of headlight leveling control and for thestabilization of the driving and the position of a vehicle.